My 6 y.o. was bitten by a tick (not sure what kind, but teeny tiny) on 6/20. I don't think it was on him very long (maybe a few hours), but I can't be 100% sure about that, obviously. He doesn't have a fever or anything, but I just noticed a red dot where the tick was attached. I don't think it was there before. It is going on 2 weeks since he was bitten, why would the dot show up now? Should I be worried about lyme or am I overreacting? The tick is very small and red, looks like a nymph to me.

I think you should have it checked out. Ticks usually have to be in for a lot longer than that to pass on Lyme disease, but since you aren't sure, it can take 2 weeks until a bullseye rash shows up. This looks like this might be a great site to get some more info. It's got pictures of the ticks, the sizes and it has pictures of the rash.